A pendulum roller is a roller mounted on an arm assembly capable of enabling that roller to swing at least limitedly about a pivot axis located above the roller and at a distance from the axis of the roller determined by the length of the arm means.
The arm means can, for example, comprise a pair of arms connected to the roller at opposite ends thereof and swingably mounted so as to pivot about a common pivot axis.
The roller may be rotatable and the web can pass around the roller.
Such pendulum rollers serve to compensate for variations in web tension which are substantially unavoidable in a winding process, whether that winding process involves a take-up of the web or a delivery of the web from a previously wound roll thereof
The web passes in a compensating loop which lengthens or contracts against the roller and thus causes the deflection thereof angularly about the pivot axis in the manner described so as to suppress pulsations in the web and render the web travel more quiescent.
The pendulum roller is urged in one angular direction or sense by the tension on the web and can be biased in the opposite direction by a fluid pressure cylinder acting on the arms, for example, to apply the requisite tension to the web.
It has been found that, especially with low web tensions and thin webs, the intrinsic weight of the pendulum roller can create problems since the intrinsic weight on small deflections contributes a restoring force urging the pendulum roller back into a dead-center position and contributing a force to the web which may be undesired.
The obvious way of eliminating this problem, of course, is to make the weight of the pendulum roller as small as possible so that the restoring force effect of this weight can be minimized. In practice, however, this does not constitute a practical solution, since the pendulum roller must have a significant axial length for very wide webs and a sufficient diameter to provide satisfactory guidance of the web.
Accordingly, the pendulum roller may have dimensions which cannot readily be limited.